对流层散射信道下多天线分集OFDM系统研究

将OFDM技术应用于对流层散射通信可以提高散射通信容量,但子载波间干扰(ICI)成为降低系统性能的主要因素,为此引入天线分集技术以抑制ICI的影响。在建立散射信道模型基础上,分析与求解了OFDM系统的ICI数学统计特性,然后引入天线分集技术,分析与推导了系统的误码率,通过仿真,对比了采用天线分集技术前后OFDM系统的误码率性能。结果表明:ICI随归一化多普勒扩展的增大而迅速增加,从而使OFDM系统产生误码平台,分集技术可以克服以上问题,在归一化多普勒频移0.02,信噪比20 dB时,2重分集能使误码率降低2个数量级以上,3重分集使误码率降低4个数量级。

An Analysis of OFDM System under Troposcatter Fading with Multi-antenna Diversity

The application of OFDM in troposcatter communication can enlarge the tropo communication capacity. Meanwhile, Inter Carrier Interference (ICI) of OFDM system is the major drawback to degrade OFDM system performance. As a result, the multi-antenna diversity techniques are introduced and the OFDM with Maximal Ratio Combining (MRC) diversity under tropo fading channel is investigated. Firstly, the tropo channel model is established, then, system ICI is investigated. OFDM system with MRC diversity under tropo channel is investigated, and the system SER is derived. Simulation results show that ICI can degrade the SER performance and introduce symbol error floor while multi-antenna diversity can solve the problem above. When normalized Doppler spread equals 0.02 and signal to noise ratio equals 20dB, dual diversity can decrease SER by two orders of magnitude and triplex diversity with four orders of magnitude.